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Treatment of cough Modified By :ISRAA
cough • Cough is a useful physiological mechanism that serves to clear the respiratory passages of foreign material and excess secretions. • It should not be suppressed indiscriminately. • There are, however, many situations in which cough does not serve any useful purpose but may, instead only annoy the patient or prevent rest and sleep.
Cough • Chronic cough can contribute to fatigue, especially in elderly patients, in such situations the physicians should use a drug that will reduce the frequency or intensity of the coughing. • Cough reflex is complex, involving the central and peripheral nervous systems as well as the smooth muscle of the bronchial tree.
Cough • It has been suggested that irritation of the bronchial mucosa causes bronchoconstriction, which in turn, stimulates cough receptors ( which probably represent a specialized type of stretch receptor) located in the tracheobronchial passages.
Types of cough • Acute cough =lasting<3 weeks • Chronic cough =lasing >8 weeks Cough may be i) Un productive (dry) cough OR ii) Productive cough (sputum)
Most common causes of cough • Common cold, • Upper/lower respiratory tract infection • Allergic rhinitis • Smoking • Chronic bronchitis • Pulmonary tuberculosis • Asthma • Gastroesophageal reflux • Pneumonia • Congestive heart failure • Bronchiectasis • Use of drugs (e.g., Angiotensin-converting enzyme inhibitors)
Treatment of Cough • Antitussives (cough center suppressants) • Expectorants • Mucolytics • Antihistamines • Pharyngeal Demulcents
1) Antitussive • Antitussive drugs act by ill defined effect in the brain stem , depressing an even more poorly defined “cough center”. • All opioid narcotic analgesic have antitussive narcotic analgesic in doses lower than those required for pain relief • They have minimum analgesic and addictive properties • Newer agent that only act peripherally on sensory nerves in bronchi are being assessed
i)CODIENE • It is the gold standard treatment for cough suppression • It decreases the sensitivity of cough center in the CNS to peripheral stimuli, decrease the mucosal secretion which thicken the sputum, and inhibit ciliary activity • These therapeutic effect occur at doses lower than those required for analgesia but still incur common side effect like constipation, dysphoria, and fatigue, in addition to addiction potential
ii) DEXTROMETHORPHAN • Is a synthetic derivative of morphine that suppresses the response of the central cough center • It has no analgesic effect, has low addictive profile, but may cause dysphoria at higher doses • Has significantly better side effect profile than codeine and has been demonstrated to be equally effective for cough suppression
2) Expectorants (Mucokinetics) • Act peripherally • Increase bronchial secretion OR • Decrease its viscosity and facilitates its removal by coughing • Loose cough ►less tiring & more productive
Classification of Expectorants Classified into a) Directly acting E.g., Guaifenesin (glycerylguaiacolate), Na+ & K+ citrate or acetate, b) Reflexly acting E.g., Ammonium salt
Directly acting expectorants i) Sodium & potassium citrate or Acetate • They increase bronchial secretion by salt action ii) Guaifenesin • Expectorant drug usually taken by mouth • Available as single & also in combination • MOA=Increase the volume & reduce the viscosity of secretion in trachea & bronchi
Reflexly acting expectorants • Ammonium salts • Gastric irritants = reflex increase in bronchial secretions + sweating
3) Mucolytics • Help in expectoration by liquefy the viscous tracheobronchial secretions • E.g., Bromhexine, Acetyl cysteine, i) Bromhexine • Synthetic derivative of vasicine MOA of Bromhexine • a) Thinning & fragmentation of mucopolysaccaride fibers • b) ↑ volume & ↓ viscosity of sputum
3) Mucolytics ii) Acetylcysteine • Given directly into respiratory tract • MOA of acetylcysteine: Opens disulfide bond in mucoproteins of sputum =↓ viscosity • Uses: • Cystic fibrosis Onset of action quick---used 2-8 hourly • Adverse effects: • Nausea, vomiting, bronchospasm in bronchial asthma
4) Antihistamines • Added to antitussives/expectorant formulation • Due to sedative anticholinergic actions produce relief from cough but lack selectivity for cough center • No expectorant action =▼secretions (anticholinergic effect) • Suitable for allergic cough • E.g., Chlorpheniramineand diphenhydramine
5) Pharyngeal demulcents • Soothe the throat (directly & also by promoting salivation • Reduces afferent impulses from inflamed/irritated pharyngeal mucosa • Provide symptomatic relief in dry cough arising from throat • E.g. lozenges, cough drops, glycerine, liquorice, honey